1. Field of the Invention
The present invention relates to an ion implantation method and more particularly to a method for implanting ions on the surface of a base material aiming at improving various characteristics such as surface hardness, abrasion resistance and corrosion resistance of the material and for implanting ions homogeneously, easily and effectively even on the surface of the inner periphery of a hole having small diameter.
2. Description of the Related Art
Methods for implanting ions on the surface of a base material have been already adopted in industries aiming at improving surface hardness, abrasion resistance and corrosion resistance of the material.
FIG. 2 is a schematic structural drawing of a typical prior art ion implanting device. The device shown in the figure comprises an ion source 11, a pull-out electrode 12 and an accelerating tube 13, a mass separator 14, a convergence deflector 15 and a sample chamber 16. These are in a vacuum system and are exhausted to a certain degree of vacuum.
At first, ions composed of atoms or molecules are created in the ion source 11. Those ions are pulled out by the pull-out electrode 12 and are introduced to the accelerating tube 13. The ions introduced to the accelerating tube 13 are then provided with desired energy and enter the mass separator 14. There, only ions having desired mass are allowed to pass through to the next convergence deflector 15. The ions are converged and deflected by a lens system and electrostatic X-Y scanner (both not shown) within the convergence deflector 15 and are homogeneously irradiated to the predetermined surface of a sample 17 set on a stage 19 within the sample chamber 16. By the way, an angle of a beam 18 deflected by the scanner is several degrees at most.
Although such prior art ion implanting device as described above can implant ions on the outside surface or shallow concave portion of a member having various shapes, it cannot implant ions on the inner wall of a deep and fine tube or on a concave hole or pore having small inner diameter (hereinafter these will be referred to as "fine hole" or "pore"). Accordingly, so far, the treatment on the inner wall of concave portion of a member have been limited only to those having a shallow depth. However, there have been many requests to implement ion implantation on the inner wall of a tubular member and on the inner wall of a fine hole or pore of a member in order to improve their characteristics. As an example of that, abrasive resistance of an injection nozzle of abrasive jet made of hard metal used for overhaul of a biological shielding wall of a nuclear reactor is desired to be improved.
In order to implement ion implantation on the surface of inner wall of such a fine tube or pore, an ion beam has to be sharply bent in the inside of the fine tube or pore. Then, Japanese Patent Laid-Open No. 61-133377 disclosed a method in which an electrical repulsive force is used to implant ions on the surface of inner wall of a hole. According to this method, a positive electrode on which high voltage is applied is inserted to the inside of the hole and ions are irradiated targeting it. The ions are then diffused by the repulsion with the positive electrode and are implanted on the surface of the inner wall of the hole.
According to the method disclosed in the aforementioned Japanese Patent Laid-Open No. 61-133377, however, it is difficult to implant ions on the inner wall of a fine tube since an electrode has to be inserted to the inside of the hole and there is a restriction regarding to the inner diameter of the material to be treated. Furthermore, there is a possibility of discharge to be caused between the material to be treated and the positive electrode. Beside those, there is such a disadvantage that since the repulsion by means of the same potential with the ion beam is used, the ions may be affected by the deceleration action and thereby ions having desired energy cannot be implanted.
Accordingly, it is a primary object of the present invention to solve the aforementioned prior art problems by providing an ion implantation method having no restriction on inner diameter of a tube, hole or pore to be treated.
It is another object of the invention to provide an ion implantation method that allows energy of an ion beam to be accurately controlled without changing the energy of the ion beam and ions to be homogeneously, easily and effectively implanted even on the surface of the inner periphery of a fine tube, fine hole or pore.